The present invention relates to an improved absorbent article and more particularly to an improved sanitary napkin. The absorbent article has both a raised central member and a pair of longitudinal raised hydrophobic edges or edge members.
Conventional full-size sanitary napkins typically include an absorbent element surrounded by a fluid pervious body facing surface and a fluid impervious undergarment facing surface. The sanitary napkin is generally attached to the user's undergarment by pressure sensitive adhesive.
The two most basic functions of a sanitary napkin are to collect menstrual fluid from the user and to prevent soiling or staining (i.e. protect) the user's under and outergarments. Conventional sanitary napkins do not completely fulfill these absorbency requirements because users experience staining of their undergarments.
Although staining occurs at different locations, side staining is the predominant failure location. Some of the different factors that lead to side staining are fluid wicking along the cover fabric or through the absorbent medium to the side edges of the napkin, lack of napkin stability, and improper fit of the napkin.
Previous attempts to address these modes of failure are described in issued patents and publications.
Canadian Patent No. 884,608 (Levesque, issued Nov. 2, 1971) describes an absorbent product having a zone treated so as to be hydrophobic extending from the outer edge of each longitudinal side of an absorbent pad. However, manufacturing this product is problematic. The process of making this entails applying a liquid repellent composition to the longitudinal sides of the pad and compressing the treated margins to distribute this composition throughout the desired hydrophobic zone. When the composition dries, the zone remains hydrophobic. However, the composition requires more time to dry than is available in a commercially viable process. Therefore, in order to maintain a high rate of production the treated products must be stacked and packaged in the wet state. This brings the treated zones of the products into contact with the walls of the packaging material. The liquid repellent then tends to adhere to the packaging as it dries, thus causing the packaging and hydrophobic zone of the pad to become inextricably attached.
U.S. Pat. No. 4,015,604 (Csillag, issued Apr. 5, 1977) describes a product having means for retarding premature failure of the product by leakage of body fluids from the side edges. A narrow zone of the absorbent element along the edges of the absorbent element but spaced away from its periphery is impregnated with hydrophobic material.
Csillag entails the same wetness/drying time encountered with the Levesque patent. Furthermore, Csillag does not address the problems of napkin instability and improper napkin fit.
Some proposed constructions for eliminating side failure suggest using plastic barriers in a "boated" configuration. European Patent Application 091,412 (Molnlycke published Oct. 12, 1983) describes an absorbent product with a raised midsection and elasticized side edges. In Molnlycke the elastic edge forms a "bowl" or "boat" surrounding the absorbent body. Because this product design incorporates a unitary absorbent structure having a cover which extends from lateral edge to lateral edge, there is a high propensity for side leakage to occur. This product design is somewhat unstable. Upon compression, the napkin may bunch, causing a depression in its center, and reducing the area of coverage. Additionally, fluid may wick along the cover to the edge of the napkin. Furthermore, the peripheral flange region of the absorbent element may tend to fold in toward the center of the napkin. Fluid then smears onto the outer edge of the flange. The flange may then contact the user's garment, causing soiling.
So called "compound" sanitary napkin designs have also been proposed to combat side failure. U.S. Pat. No. 2,662,527 (Jacks, issued December 1953), describes an absorbent pad having a main body member composed of absorbent material and a second absorbent portion secured on the face of the main member. The second portion is narrower and shorter than the main body member and has dimensions which allow it to fit between the labia. The second portion is intended to be held against the vaginal orifice such that fluid is absorbed at the point of discharge from the body. The bottom section of the napkin is held in place with a sanitary belt or a supporter. Jacks intended the small top pad to provide a damming action to retard leakage of fluid toward the rear of the user. The main body member was to engage the body at a point near the rectum to provide a second damming action. Although this system provides means to capture the fluid, fluid may still flow from the second absorbent portion to the main body member. During use, the longitudinal edge of the main member may fold in and contact the soiled edge of the top member. After returning to its original state, the stained edge of the main member may contact the edge of the undergarment crotch.
Another compound sanitary napkin design having two discrete layers is described in U.S. Pat. No. 3,406,689 (Hicks, issued Oct. 22, 1968). These two pads are separate from one another and are freely movable with respect to each other. The first pad, or contact pad, is intended to be pressed against the body of the user while the second pad extends over the genitalia and anal portions of the user. Both pads contain absorbent material. Positioning and discarding these two pads may be time consuming and messy. Fluid may also travel from the contact pad to the edge of the backup pad, resulting in napkin failure.
U.S. Pat. No. 4,425,130, (DesMarais, issued Jan. 10, 1984) also describes a two-pad napkin design. A primary menstrual absorbent pad and a "panty protector" pad are joined such that there is a continuous section spanning at least 75% of the common length uninterrupted by points of attachment. The primary absorbent pad is intended to absorb and retain menstrual fluid. The panty protector member is meant to protect the user's garments from being soiled by fluids which are expelled from the primary menstrual pad or which inadvertently pass the primary pad. This construction does not compensate for the deficiencies of two-pad systems discussed above.
Structural napkin instability also causes side failure. Compressive forces, such as those exerted by a user's thighs, tend to cause the napkin applied to a napkin, to fold or bunch, reducing the area of coverage and interrupting contact between napkin and body. Thus, body fluid may be deposited on the side edge of the napkin, resulting in napkin failure. U.S. Pat. No. 4,195,634 (Di Salvo, issued Apr. 1, 1980) describes resilient and/or stabilized absorbent systems designed to address this problem. However, Di Salvo does not disclose a raised central member.
Another result of a compressive force is that the undergarment rises up around the sides of the napkin and contacts the napkin face, especially if the width of the undergarment crotch is greater than the sum of the napkin width and the thickness of each edge. McNair, U.S. Pat. No. 4,285,343 and Van Tilburg, U.S. Pat. No. 4,589,876 describe designs that address this mode of failure.
McNair teaches a central elongate absorbent element with laterally extending side panels. The side panels are folded over on the outer surface of the crotch section of an undergarment in order to keep the central element of the napkin from sliding. McNair does not discuss fluid wicking.
Van Tilburg teaches a sanitary napkin that includes a central absorbent pad with flaps extending from each of its longitudinal edges. Each flap has a flexible axis located in the body of the flap which allows the flap to be folded on itself. It is possible for fluid to wick to the longitudinal edges of Van Tilburg. The negative attributes associated with this 2-flap design includes a cumbersome attachment and removal system and lack of comfort for the user during use.
When improper fit of the napkin occurs fluid travels along the body and bypasses the sanitary napkin. When the napkin is away from the user, fluid tends to travel along the contours of the body. The result is that soiling of the user's undergarment crotch may occur at the side edge or at the front and/or back of the undergarment.
In response to the improper fit of napkins some patents discuss napkins in which the central region contains additional absorbent or is thicker than the sides of the napkin. One such patent is Pierce, U.S. Patent No. 4,490,147 which describes a raised center sanitary napkin comprising elongate absorbent pads which are arranged parallel to one another in a pyramid shaped bundle. These pads are moveable with respect to one another and are encased by a liquid pervious cover material. Although there are discrete absorbent zones, the cover encompasses these in such a way that the product functions as a unitary structure. It is possible for fluid to wick along the cover to the napkin edge. Also because of the pyramid shape it is likely that fluid would "roll off" the napkin edge, hence, causing soiling of the user's undergarment. Although this design addresses fit, it does not have the features necessary to provide adequate protection.
U.S. Pat. No. 3,969,187 (Glassman) describes a napkin embodying a longitudinal, centrally located rib or ridge on its top surface adapted to enter the vaginal cleft. The central ridge and the pad surface on either side of the ridge are provided with a multiple of deep spaced-apart channels to increase the lateral compressibility of the marginal surfaces and the ridge. However, there is no provision for preventing side failure.
Another patent that attempts to alleviate the problems that arise from factor three is Molnlycke, which was discussed above.